Narcissus

(The). This charming flower is named from the son of
Cephisus. This beautiful youth saw his reflection in a fountain, and
thought it the presiding nymph of the place. He tried to reach it, and
jumped into the fountain, where he died. The nymphs came to take up the
body that they might pay it funeral honours, but found only a flower,
which they called Narcissus, after the name of the son of Cephisus. (Ovid's Metamorphoses, iii. 346, etc.)

Plutarch says the plant is called Narcissus from the Greek narke (numbness), and that it is properly narcosis, meaning the plant
which produces numbness or palsy.